While initial public panic about the swine flu outbreak has largely subsided, the virus continues to spread through our species: The World Health Organization has tallied more than 10,000 cases worldwide, with 80 deaths confirmed. As patterns begin to emerge regarding who gets infected with the H1N1 flu virus, health officials are beginning to map out strategies for a potential wide-spread vaccination campaign.

Young people are particularly prone to infection, researchers say. Preliminary studies of family transmission showed that when one member gets infected, the most likely to follow are those under 18, not parents or grandparents [The New York Times]. The virus’s spread through the young has led to the closing of schools in infection hotspots–Japan is the most recent country to shut school doors–but most cases in young people have not been severe. The people who do get more serious cases that lead to hospitalization have tended to have underlying health conditions like heart problems, lung ailments, immune diseases, and diabetes. Surprisingly, obesity has also emerged as a risk factor.

Researchers says the link between obesity and more severe swine flu may be explained by physical pressure on the lungs. Studies have shown that pregnant women are also at higher risk for serious influenza infection, especially in the third trimester, when the fetus and womb compress the lower parts of the lungs. This makes it harder to breathe deeply and cough forcefully; it may also alter blood flow in the chest. A similar thing may be occurring in severely overweight people, some experts speculated [Washington Post]. If a wide-spread vaccination campaign is launched, it’s possible that obese people will join other high-risk groups at the front of the line, say officials from the Centers for Disease Control and Prevention.

The outbreak’s spread to Japan has alarmed Asian health officials, who warn that the virus may have already reached Tokyo, which with almost 36 million people is the world’s most populous urban area. Face masks have become ubiquitous on buses, commuter trains and in shopping centres of affected areas in Japan where 228 people have been infected. Many of the cases have been among school students, prompting authorities to close more than 4,400 schools, colleges and kindergartens for the rest of the week to slow the spread of the virus [AFP].

WHO officials have asked vaccine makers who usually turn out seasonal flu vaccines to develop batches of a swine flu vaccine for testing, although the organization has not yet asked the companies to launch a full-scale manufacturing effort. WHO officials say that drug makers could potentially turn out 4.9 billion doses of vaccine within a year, and note that they’re taking steps to be sure that vaccines aren’t monopolized by richer countries. WHO Director-General Dr. Margaret Chan told reporters after a meeting with 30 pharmaceutical companies that WHO was working to secure supplies of vaccine for poor countries in case of a pandemic…. Six companies have pledged to make 10 percent of the vaccine they produce available for distribution to poor countries, and eight are in talks about donations [Reuters].

228 out of 150… million? Considering the fairly low mortality rate so far I’d say the current dust-up over this is… a little out of proportion. In fact, I’m pretty sure flus like this have been spreading quite regularly around the world, just going un-noticed due to lack of methods to discover them until recently.

Honestly, if we didn’t know if was any different than regular influenza, would anyone notice a thing? “Regular” flu has a mortality rate of 0.1% and according to the numbers quoted above, the current H1N1 has a mortality rate of … 0.008%

Although the H1N1 infection has caused severe morbidity and mortality in only a relatively small percentage of infected people to date, this does not exclude the possibility that the H1N1 strain could mutate to a more virulent form. The greater the number of people infected, the greater is the chance of this occurring. Influenza is, as you know, renowned for its ability to mutate. The longer H1N1 remains uncontained /’in the wild’ the greater is the chance that it might mutate to a more virulent strain. This has apparently been the pattern of other pandemics of influenza: an initial low morbidity and low mortality phase followed soon thereafter by a highly virulent phase with a large spike in severe illness and mortality. [The 1918 pandemic resulted in approximately 40 million deaths.]

Nick, as regards research into cancer and HIV, i am with you on that! It is conceivable however imo that research into influenza A mutations (with their attendant permutations and combinations of variable viral markers) might possibly lead to promising new leads into the research and treatment of HIV/AIDS, as well as some forms of cancer.

bongwater

The Chicago Sun Times said that this batch of swine flu has circulated 10 years in pigs.

In 1918 50% of pregnant women died.

How many more people would be on the Earth today if those 40,000,000 would have survived and bred since 1918? Don’t get me wrong, I am no PETA eugenicist. With another 150-200,000,000 people here things’d look a lot different than they do now.

michel

I just wanted to comment that 80 deaths have been confirmed of the 10,000 cases of known swine flu. That number represents a 0.008 mortality rate or a 0.8 percent mortality rate. Not the 0.008 percent mortality rate that Nick figured. And the number of confirmed deaths is admittedly conservative and only represents a fraction of the real figure as reports of confirmed cases will always lag behind the actual number of infection related deaths. Perhaps this variety of flu does not seem any more significant than the seasonal flu but there is reason to be cautious. We know what to expect from the seasonal flu. H1N1 has elements that are a human, pig and bird flu in origin. We know that transmission occurs between human and pig. What about human and bird transmission? I think that if we discover birds can carry H1N1 then we have a potential problem. We know this virus has a strong ability to integrate new genetic code….that it mutates easily. What if it were to combine genetically with that of H5N5 (avian flu)?….Would that be possible?

Wayne

Michel, thanks! Imo you’ve made some very salient points here re H1N1. What you said has clarified, in plain language, some very important things about the Influenza A virus and why major mutations (antigenic shift) in the Inflenza-A virus can lead to highly virulent new strains.

Saul Wilson

It has a low lethality rate because it has not yet adapted to the lower respiratory tract like Avian flu already has. But it is novel so no one has an immunity (except maybe older folk with partial immunity due to being exposed to an H1N1 virus when it was active as a seasonal flu).

If a strain of this virus adapts to work both in the upper and lower tract it would be more deadly while still being highly communicable. If deep respiratory infection increased coughing, propelling aerosols generated in the upper respiratory tract further, it could work to increase transmission even further.

A selective pressure favoring a novel virus to become more lethal not only sounds like something worth striving against but would explain the “herald wave” phenomenon where a lethal pandemic is preceded by a mild wave.

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